A radiating element used in an antenna of a base station, including a repeater of a wireless communication system, is applied with various types of radiating elements, such as a patch type and a dipole type. Among them, the dipole-type radiating element has two radiating arms forming the poles corresponding to each other, and generally, the length of each pole (radiating arm) is set as ¼λ (λ: wavelength) of the wavelength of the used frequency, and a total length of the two radiating arms is composed of ½λ. Recently, the wireless communication antenna is generally implemented as a dual-polarized antenna structure by applying a polarized diversity manner, and the dipole-type radiating element is widely used for the dual-polarized antenna because the structure for generating two (orthogonal) polarized waves is easily implemented and the arrangement of the radiating element is easy.
FIGS. 1A to 1C are configuration views of a general dipole-type radiating element; and FIG. 1A illustrates a physical model thereof, FIG. 1B illustrates an equivalent structure indicating a current flow path in FIG. 1A and FIG. 1C illustrates current distribution in FIG. 1A. The dipole-type radiating element illustrated in FIGS. 1A to 1C is implemented as one dipole element, and forms a balun structure using a structure of a basic coaxial line 11. An inner conductor 112 of the coaxial line 11 is connected with a first radiating arm 122, and an outer conductor 114 is connected with a second radiating arm 124 to overall implement a half-wave dipole-type radiating element.
FIG. 2 is a first exemplary configuration view of the conventional dipole-type dual-polarized radiating element, and illustrates the structure that can be seen as a basic model of a dual-polarized radiating element generating a so-called ‘X-polarized wave’. The dual-polarized radiating element in FIG. 2 is the structure that two dipole elements of the structure illustrated in FIGS. 1A to 1C are perpendicular to each other at an angle of 90 degrees, and can be overall implemented as a ‘X’ shape. That is, a first dipole element is composed of a 1-1 radiating arm 222 connected with an inner conductor 212 of the first coaxial line and a 1-2 radiating arm 224 connected with an outer conductor 214 of the first coaxial line, and is installed at an angle of +45 degrees with respect to the vertical axis (or the horizontal axis). A second dipole element is composed of a 2-1 radiating arm 322 connected with an inner conductor 312 of the second coaxial line and a 2-2 radiating arm 324 connected with an outer conductor 314 of the second coaxial line, and is installed at an angle of −45 degrees with respect to the vertical axis (or the horizontal axis). In this case, the first coaxial line and the second coaxial line are configured to receive a feeding signal as a separate signal source, respectively. Examples of the dipole-type dual-polarized antenna are disclosed in the U.S. Pat. No. 6,034,649 (Title: “DUAL POLARIZED BASED STATION ANTENNA,” Registered Date: Mar. 7, 2000) by ‘Andrew Corporation,’ or the Korean Patent Application No. 2000-7010785 first filed by ‘Kathrein-Verke AG’ (Title: “DUAL-POLARIZED MULTI-BAND ANTENNA,” Filed Date: Sep. 28, 2000).
The dipole-type dual-polarized antenna as illustrated in FIG. 2, as the shape corresponding to a basic model, is proposed as various structures for balun and feeding structures, etc., including the radiating arms of the dipole element, considering the enhancement of radiating performance, the improvement of broadband or narrowband radiating characteristics, the optimized size and shape, the manufacturing process and the installation costs, etc. For example, as illustrated by the dotted line in FIG. 2, particularly, the radiating arms of the dipole element can have various structures, such as a ring shape of a square, or a plate shape of a square, or a ribbon shape, etc. as well as simply a linear rod shape.
FIG. 3 is a second exemplary configuration view of the conventional dipole-type dual-polarized radiating element, and proposes the structure that modifies the structure of the radiating arms and the feeding structure in comparison with FIG. 2. The dipole-type dual-polarized radiating element illustrated in FIG. 3 is implemented by first and second dipole elements that are perpendicular to each other in a ‘X’ shape, a first dipole element includes the 1-1 and 1-2 radiating arms 242, 244, and a second dipole element includes the 2-1 and 2-2 radiating arms 342, 344. In this case, it is illustrated that the radiating arms 242, 244, 342, 344 of the first and second dipole elements have, for example, a plate shape of a square in order to have the characteristic of the broadband.
Furthermore, the feeding structures of the first and second dipole elements do not have the structure using the coaxial line as illustrated in FIG. 2, but have a structure of a stripline transmission line. That is, in the structure illustrated in FIG. 3, feeding conductor portions of the feeding lines are composed of first and second striplines 232, 332. The first stripline 232 is placed along a support fixture of a balun structure forming a ground portion of the feeding line while supporting the 1-1 radiating arm 242, the first stripline 232 is extended to a support fixture of the 1-2 radiating arm 244 to deliver, for example, a feeding signal to the 1-2 radiating arm 244 in a capacitance coupling manner. Likewise, the second stripline 332 is placed along a support fixture of the balun structure supporting the 2-1 radiating arm 342, and is extended to a support fixture of the 2-2 radiating arm 344 to deliver a feeding signal to the 2-2 radiating arm 344.
FIGS. 4A to 4D are third exemplary configuration views of the conventional dipole-type dual-polarized radiating element; and FIG. 4A is a plane view, FIG. 4B is a perspective view seen at an upper side thereof, FIG. 4C is a perspective view seen at a lower side thereof, and FIG. 4D is a separate perspective view with respect to the striplines of FIGS. 4A to 4C. The dual-polarized radiating elements illustrated in FIGS. 4A to 4D are composed of a first dipole element including the 1-1 and 1-2 radiating arms 262, 264 and a second dipole element including the 2-1 and 2-2 radiating arms 362, 364. In this case, the radiating arms 262, 264, 362, 364 of the first and second dipole elements have the structure adding the structure of a ring shape of a square to the structure illustrated in FIG. 2, for example, in order to have the characteristic of the broadband to thus overall have the structure of a square shape.
The feeding structures of the first and second dipole elements illustrated in FIGS. 4A to 4D have the structure of the stripline transmission line as illustrated in FIG. 3. That is, the first stripline 252 is placed in the shape that is extended from the support fixture of the 1-1 radiating arm 262 to the support fixture of the 1-2 radiating arm 264 to deliver a feeding signal to the 1-2 radiating arm 264. Likewise, a second stripline 352 is placed in the shape that is extended from the support fixture of the 2-1 radiating arm 362 to the support fixture of the 2-2 radiating arm 364 to deliver a feeding signal to the 2-2 radiating arm 364. In this case, as more clearly illustrated in FIG. 4D, the intersection of the first and second striplines 252, 352 is installed in the shape of an air bridge in order not to be connected with each other.
FIG. 5 illustrates a plane structure as a fourth exemplary configuration view of the conventional dipole-type dual-polarized radiating element. The dual-polarized radiating element illustrated in FIG. 5 is composed of a first dipole element including 1-1 and 1-2 radiating arms 282, 284, and a second dipole element including 2-1 and 2-2 radiating arms 382, 384. In this case, each of the radiating arms 282, 284, 382, 384 of the first and second dipole elements has a ‘’ shape that is bent at the center of the plane structure thereof; and each of the bent portions is sequentially adjacent to each other and has the structure that is overall arranged in the ‘’ shape in a four-way symmetrical manner on a plane. That is, each of the radiating arms 282, 284, 382, 384 can have the structure similar to that of two sub-radiating arms connected to each other at an angle of 90 degrees.
Furthermore, the feeding structures of the first and second dipole elements have the structure of the stripline transmission line as illustrated in FIGS. 3 and 4; and a first stripline 272 is placed in the shape that is extended from a support fixture provided in the bent portion of the 1-1 radiating arm 282 to a support fixture provided in the bent portion of the 1-2 radiating arm 284. Likewise, a second stripline 372 is placed in the shape that is extended from a support fixture provided in the bent portion of the 2-1 radiating arm 382 to a support fixture provided in the bent portion of the 2-2 radiating arm 384.
Examples of the dipole-type dual-polarized antenna having the structure illustrated in FIG. 5 can be disclosed in the Korean Patent Application No. 2011-9834 first filed by the Applicant of the present disclosure (Title: “DUAL-POLARIZED ANTENNA FOR WIRELESS COMMUNICATION BASE STATION AND MULTI-BAND ANTENNA SYSTEM USING THE SAME,” Date of Patent: Jun. 8, 2004), or the U.S. Pat. No. 6,747,606 (Title: SINGLE OR DUAL POLARIZED MOLDED DIPOLE ANTENNA HAVING INTEGRATED FEED STRUCTURE,” Registered Date: Jun. 8, 2004) by ‘Radio Frequency Systems’.
As described above, in order to implement the multi-polarized radiating element, various researches have been currently proceeded considering the radiating performance and characteristics, the shape and size, the manufacturing manner, ease of design, etc. Particularly, various structures for balun and feeding structures including the radiating arms of the dipole element have been proposed.